Various methods have been used to interpret specific dipping surfaces, namely, faults and fractures. These interpretation methods are applied to images obtained from various borehole imaging tools. Examples of the available tool technology and potential sources for such tools includes, but is not limited to: wireline technology, such as resistivity/conductivity imaging using conductive muds (e.g., Schlumberger's FMI & FMS, Baker Atlas' STAR, Halliburton's EMI & XRMI, Weatherford's HMI & CMI), and non-conductive muds (e.g., Schlumberger's OBMI, Baker Atlas' EARTH, Halliburton's OMRI); azimuthal resistivity imaging (e.g., Schlumberger's ARI); acoustic/sonic imaging (e.g., Schlumberger's UBI, Baker Atlas' CBIL, Halliburton's Cast-V); and logging while drilling technology, such as gamma ray imaging, density imaging (e.g., Schlumberger's ADN, Baker Inteq's LithoTrak, and Weatherford's AZD, Halliburton's ALD), and electrical/resistivity imaging (e.g., Schlumberger's Geovision, Baker Inteq Star Trak, and Halliburton's AFR).
Numerous commercial software packages specifically developed for the processing, display and extraction of geological data from borehole images are currently available (e.g., Petris' RECALL™, TerraSciences' TerraStation™). Further, methodologies for the identification and trigonometric measurement of dipping, planar surfaces in borehole images are already well established. See e.g., U.S. Pat. No. 5,960,371. However, the specific terminology used in the subsequent description and interpretation of such surfaces varies, and is in many cases equivocal and/or subjective.
The terminology used to describe the features identified and measured is usually left to the discretion of the individual operator/geologist, or to internal procedures established with their organization. The terminology may be related to the appearance of the feature being identified or measured, according to the specific tool physics used in the particular borehole image being analyzed. Such terminology may be descriptive, but is generally only valid for the specific data being analyzed and for one, or perhaps more than one, tool type.
As a result, the terminology currently used could impart different meanings to a reader, depending upon their background and/or level of understanding of that terminology. Table 1 below, summarizes the commonly used interpretation terminology.
TABLE 1Commonly Used Interpretation TerminologyCurrent Terminology,As Applied To FractureAnd Fault PlanesCommentsOpenThese terms are ten examples ofClosedinterpretive terminology that relies uponCementedthe subjective opinion of the individualMineralizedoperator or geologist analyzing theHealedborehole image to identify variousSheargeological features. Due to the subjectiveStressnature of these terms, individual operatorsMixedor geologists are often free to create newPartially Opencategories “on the fly.”Partially CementedResistiveThese terms are six examples of tool-Conductivefeature terminology that is specific to theHigh Amplitudevarious borehole imaging tool-typesLow Amplitudeemployed, and may, or may not be,Fastapplicable from one tool technology toSlowanother. This tool-feature terminologyassumes an intimate knowledge of theborehole imaging technology being used,and, therefore, the terms are prone tomisinterpretation outside the immediateborehole imaging community.Open/ConductiveThese terms are two examples of hybridCemented/Resistiveterminology that attempt to include tool-related features and geologicalinterpretation. Again, these terms aresubject to differences in interpretation.
Thus, an interpretation method is needed that may be applied to images obtained from any borehole imaging tool regardless of tool physics or acquisition type, and that is compatible with any of the commercial software packages specifically developed for the processing, display and extraction of geological data from borehole images, and that is independent of the tool technology used to obtain such borehole images.